1. Technical Field of the Invention
This invention relates to a method and an apparatus for removing contamination adhered to the surface of a substrate, such as a semiconductor wafer or a LCD substrate.
2. Description of the Related Art
In manufacturing semiconductor devices, there is a need to improve the degree of cleanliness of the surface of the semiconductor wafer that comprises the semiconductor device. To this end, the wafer surface is cleansed before and after each process is carried out. Particularly, as cleansing prior to conducting the photolithography process is vital, particles and other contamination adhering to the surface of the wafer are removed via scrub cleaning. Scrub cleaning is carried out by supplying a cleansing solution to the surface of the revolving wafer, and simultaneously causing a revolving brush to contact the wafer, moving it from the center to the outer edge of the wafer surface.
In recent years, the size of wafers has been increasing. When cleansing such a larger wafer, moving a single brush repeatedly across the surface does not improve the cleansing efficiency, and lengthens the amount of time required for the cleansing process.
With the cleansing apparatus disclosed in Japanese patent laid open publication No. 10-308370A, in order to increase throughput, two identical scrub brushes are used to cleanse the wafer surface. However, when cleansing is carried out by having two identical brushes contact the wafer surface, contamination removed by one of the brushes sometimes adhere to the other brush, and are thus re-applied to the wafer surface (we call this phenomenon “particle-transfer”). As a result, in order to remove the re-applied contamination, the cleansing operation must be carried out repetitively. Due to this, not only is the amount of time required for the cleansing process increased, the wafer surface may be damaged due to excessive cleansing. Furthermore, in order to restore the functionality of the brushes, they themselves must be cleansed for a considerable amount of time after each usage (cleansing of the wafer surface). In addition, if the cleansing process time is lengthy, deterioration of the brushes, such as wear and tear, deformity, etc., will progress and the frequency of having to stop operation of the apparatus in order to replace the brushes will therefore increase.